Biomaterials have the potential to significantly impact medicine as delivery systems for imaging agents, biosensors, drugs, and genes. Farokhzad O C. Nanotechnology for drug delivery: the perfect partnership. Expert Opin Drug Deliv 2008; 5(9):927-9; Putnam D. Polymers for gene delivery across length scales. Nat Mater 2006; 5(6):439-51; Brigger I, Dubernet C, Couvreur P. Nanoparticles in cancer therapy and diagnosis. Adv Drug Deliv Rev 2002;54(5):631-51. Challenges exist, however, in creating a delivery vehicle capable of effective, safe, and controlled release of sensitive biomolecules. Although rapid advances have been made for sustained delivery of small molecule drugs using biotechnology, similar advances have not been made for the delivery of peptides, siRNA, or combinations of biological agents.